Disclosed are various embodiments that facilitate client-side encryption of form data. A network page that includes client-side code that encrypts one or more data items using a public key is sent to the client. The data items are provided by a user in one or more form fields of the network page. The data items and one or more unencrypted data items are obtained from the client over an encrypted channel. The data items are encrypted using the public key when the data items have not been encrypted by the client-side encryption code. The data items are sent in an encrypted state to a server over an internal network. A firewall is interposed between the internal network and the server to protect the server from the internal network.